Automatic transmissions, especially for motor vehicles, encompass, in accord with their state of the technology, planetary gear sets. Further the transmissions are shifted by means of friction elements or shifting elements, such as clutches and/or brakes and normally possess a start-up element. The start-up element is subjected to slip action and optionally has a converter lock-up clutch, somewhat in the manner of a connection with a hydrodynamic torque converter or a fluid clutch.
Within the general framework of DE 101 15 983 A1, the applicant, for instance, has described a multi-speed transmission having an input shaft, which is connected to an input-side planetary gear set and being further equipped with an output shaft, which is connected to an output side planetary gear set. The described multi-speed transmission also has a maximum of seven shifting elements, by means of the selective shifting thereof, seven forward gears can be implanted, without the intervention of range-shifting. The input side planetary gear set is constructed from a shiftable or a non-shiftable planetary gear set, or alternately, from a maximum of two non-shiftable, mutually coupled planetary gear sets. The output side planetary gear set is designed as a two carrier, four shaft transmission with two shiftable planetary gear sets and possesses four free shafts. The first free shaft of this two carrier, four shaft transmission is bound to the first shifting element, the second free shaft connects with the second and third shifting elements, the third free shaft is connected to the fourth and fifth shifting elements and the fourth free shaft is bound with the output shaft. In the case of a multi-speed transmission, which has a total of six shifting elements, in accord with the invention, the proposal is made, that the third free shaft or the first free shaft of the output sided planetary gear set, should be bound additionally to a sixth shifting element. With a multi-speed transmission having a total of seven shifting elements, in accord with the invention, a proposal is made, that the third free shaft be connected to sixth shifting element and the first free shaft be additionally connected to a seventh shifting element.
A plurality of other multi-speed transmissions are, for example, also disclosed by DE 101 15 995 A1 of the applicant, wherein four shiftable, mutually coupled planetary gear sets and six or seven friction-based shifting elements are provided, by the selective closure thereof, the speed of rotation of the input shaft of the transmission is so transferred to the output shaft of the transmission, such that nine or eleven forward gears may be implemented and at least one reverse gear can be shifted into. In accord with the shifting diagram (FIG. 2), it is seen, that in each gear, two or three shifting elements are closed, whereby, by means of a change from one gear to another gear which is immediately the next higher or lower gear therefrom, in order to avoid group shifting, the shifting is completed by disengaging only one engaged shifting element and a previously disengaged shifting element is engaged.
Additionally, in the generic, unpublished patent application, namely, DE 102005002337.1 of the applicant, a multi-speed transmission is proposed, which possesses one input shaft, one output shaft, four mutually coupled individual planetary gear sets along with five shifting elements, whereby, eight forward gears are accessible without range shifting and also the proposal is such that when changing from one forward gear to the immediately next successive higher or lower forward moving gear, only one of the previously engaged shifting elements need be opened and only one of the previously disengaged shifting elements need be engaged. The multi-speed transmission also possesses a reverse gear. In all forward-travel gears and in the single reverse gear, respectively, three shifting elements are engaged. Considering the kinematic coupling of the four planetary gear sets among each other and the two shafts, namely for input and output, provision is made, that: a carrier of the fourth planetary gear set and the input shaft are bound together and form a first shaft of the transmission, a carrier of the third planetary gear set and the output shaft are bound together and form a second shaft of the transmission, a sun gear of the first planetary gear set and a sun gear of the fourth planetary gear are connected together to form a third shaft of the transmission, a ring gear of the first planetary gear set forms a fourth shaft of the transmission, a ring gear of the second planetary gear set and a sun gear of the third planetary gear set are bound together and form a fifth shaft of the transmission, a carrier of the first planetary gear set and a ring gear of the third planetary gear set are bound together and form a sixth shift of the transmission, a sun gear of the second planetary gear set and a ring gear of the fourth planetary gear set are bound together and form a seventh shaft of the transmission, and a carrier of the second planetary gear set forms an eighth shaft of the transmission. Further, considering the kinematic coupling of the fifth shifting element to the four planetary gear sets and to the input and output shafts, it is provided that placements are made, so that: the first shifting element in the power flow is between the third shaft and the transmission housing, the second shifting element is between the fourth shaft and the transmission housing, the third shifting element is between the first and fifth shafts, the fourth shifting element is either between the eighth and second shafts, or between the eighth and sixth shafts, and the fifth shifting element is either between the seventh and fifth shafts or between the fifth and eighth shafts.
Automatically shiftable vehicle transmissions, which are based on planetary gear sets, have, in general, been described many times in terms of the state of the technology and form the foundation of an on-going development and improvement thereof. These transmissions should possess a sufficient number of forward gears along with a single reverse gear and provide, for a motor vehicle, a very well adapted ratio selection with an advantageous spread. Further, these transmissions should enable high start-up ratios in the forward direction and should be suitable for installation both in passenger cars as well as in commercial vehicles. Beyond this, these transmissions should require a relatively small investment of money and labor for assembly, a relatively small number of shifting elements and sequential shifting arrangements for double clutching should be avoided. The result is, that in case of shifting in defined gear-groups, only one shifting element need be operated.